Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$116.38	12.213%	$130.5935	$130.59	$130.60	$130.60
Purchase #2	$50.77	13.839%	$57.7961	$57.80	$57.80	$57.80
Purchase #3	$81.43	5.351%	$85.7873	$85.79	$85.80	$85.80
Purchase #4	$170.73	6.516%	$181.8548	$181.85	$181.85	$181.90
Purchase #5	$206.82	5.562%	$218.3233	$218.32	$218.30	$218.30
Purchase #6	$147.28	5.192%	$154.9268	$154.93	$154.95	$154.90
Purchase #7	$242.33	11.276%	$269.6551	$269.66	$269.65	$269.70
7 purchase totals =	$1,015.74		$1,098.9369	$1,098.94	$1,098.95	$1,099.00